You can’t fix a misunderstanding by being louder. Try being clearer.

Repeating yourself with more force adds pressure, not information. If the words did not land the first time, the second time at twice the volume contains exactly the same gap, plus a reason for the other person to stop listening. Loudness feels like effort, which is why it is such a tempting substitute for thinking.

When you are not getting through, change the sentence rather than the volume. Say it in different words, give an example, or ask the other person what they think you just said. That last question sounds strange the first time and finds the actual misunderstanding about half the time.